Electronic switch module with oppositely-arranged power switches and discrete heat sinks

ABSTRACT

An electronic module is provided including a circuit board defining a longitudinal axis and having a first surface and a second surface. A module housing is provided having a bottom surface and side walls extending from the bottom surface to form an open face through which the circuit board is received. Power switches configured as an inverter circuit to drive an electric motor are mounted on the second surface of the circuit board facing the bottom surface of the module housing, and a series of heat sinks are discretely mounted on the first surface of the circuit board facing the open face opposite the power switches. Potting material is disposed in the distance between the circuit board and the bottom surface of the module housing to cover the power switches. Thermal vias are disposed through the circuit board between corresponding ones of the heat sinks and the power switches.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/691,160 filed Jun. 28, 2019, which is incorporated by reference inits entirety.

FIELD

This application relates to an electronic module, and in particular toan electronic module coupled to a trigger switch for activating a motorin a power tool.

BACKGROUND

A brushless DC motor includes a rotor for providing rotational energyand a stator for supplying a magnetic field that drives the rotor.Comprising the rotor is a shaft supported by a bearing set on each endand encircled by a permanent magnet (PM) that generates a magneticfield. The stator core mounts around the rotor maintaining an air-gap atall points except for the bearing set interface. Included in the air-gapare sets of stator windings that are typically connected in either athree-phase wye or Delta configuration. Each of the windings is orientedsuch that it lies parallel to the rotor shaft. Power devices such asMOSFETs are connected in series with each winding to enable power to beselectively applied. When power is applied to a winding, the resultingcurrent in the winding generates a magnetic field that couples to therotor. The magnetic field associated with the PM in the rotor assemblyattempts to align itself with the stator generated magnetic fieldresulting in rotational movement of the rotor. A control circuitsequentially activates the individual stator coils so that the PMattached to the rotor continuously chases the advancing magnetic fieldgenerated by the stator windings. A set of sense magnets coupled to thePMs in the rotor assembly are sensed by a sensor, such as a Hall Effectsensor, to identify the current position of the rotor assembly. Propertiming of the commutation sequence is maintained by monitoring sensorsmounted on the rotor shaft or detecting magnetic field peaks or nullsassociated with the PM.

In conventional power tools utilizing a universal motor or a brushedpermanent magnet motor, a contact switch is typically disposed on thecurrent path from the power source to the motor. U.S. Pat. No.6,717,080, filed May 22, 2003, described a trigger assembly coupled to apower contact switch on the current path of the motor. Actuation of thetrigger by a user closes the contact switch. The contact switch isspring-loaded to reopen once the trigger is released by the user.

US Patent Pub. No. 2015/0280515, filed Mar. 30, 2015, content of whichis incorporated herein by reference in its entirety, describes anintegrated switch and control module for driving a brushless DC (BLDC)motor in a power tool. This module, in an embodiment, includes a planarcircuit board that accommodates a controller, a series of power switchesconfigured as a three-phase inverter circuit, a series of correspondingheat sinks mounted on the power switches, and an input unit coupled to atrigger. In this module, the controller deactivates the inverter circuitwhen the trigger is not actuated. Specifically, the initial actuation ofthe trigger generates a signal to power the controller, but thecontroller does not begin to switch the inverter circuit ON untilfurther actuation of the trigger. With this arrangement, a separatepower contact switch need not be provided, which is important given thespace limitations associated with placement of a power contact switch inan integrated switch and control module. However, in the event of afailure of the controller or the power switches, the motor issusceptible to run unintentionally, which is a risk to the users.

This section provides background information related to the presentdisclosure and is not necessarily prior art.

SUMMARY

According to an embodiment of the invention, an electronic module isprovided. The electronic module includes a circuit board defining alongitudinal axis and having a first surface and a second surface. Amodule housing is provided having a bottom surface and side wallsextending from the bottom surface to form an open face, where the modulehousing receives the circuit board through the open face and retains thecircuit board within the side walls substantially parallel to the bottomsurface and at a distance from the bottom surface. Power switchesconfigured as an inverter circuit to drive an electric motor are mountedon the second surface of the circuit board facing the bottom surface ofthe module housing, and a series of heat sinks are discretely mounted onthe first surface of the circuit board facing the open face opposite thepower switches. Potting material is disposed in the distance between thecircuit board and the bottom surface of the module housing to cover thepower switches. Thermal vias are disposed through the circuit boardbetween corresponding ones of the heat sinks and the power switches.

According to an embodiment, the power switches include high-side powerswitches disposed between a positive node of a power supply and theelectric motor, and low-side power switches disposed between a negativenode of the power supply and the electric motor.

According to an embodiment, electronic module includes a main conductivetrack disposed on the first surface of the circuit board providing amounting surface for three of the heat sinks that correspond to thehigh-side power switches, and the main conductive track electricallycouples the three heat sinks corresponding to the high-side powerswitches to the positive node of the power supply.

According to an embodiment, the main conductive track includes an axialportion that extends along the longitudinal axis of the circuit boardand on which three of the heat sinks are mounted, and a traversalportion arranged downstream from the heat sinks in the direction of thelongitudinal axis of the circuit board.

According to an embodiment, a series of discrete conductive tracks thatare electrically-isolated are disposed on the first surface of thecircuit board along a row parallel to the longitudinal axis of thecircuit board. The discrete conductive tracks provide mounting surfacesfor three of the heat sinks corresponding to the low-side powerswitches.

According to an embodiment, a first group of power switch conductivetracks are disposed on the second surface of the circuit board oppositethe main conductive track to provide mounting surfaces for the high-sidepower switches, and a second group of power switch conductive tracks aredisposed on the second surface of the circuit board opposite the row ofdiscrete conductive tracks to provide mounting surfaces for the low-sidepower switches.

According to an embodiment, drains of the high-side power switches areelectrically connected to the first group of power switch conductivetracks, and the thermal vias electrically couple the main conductivetrack to the first group of power switch conductive tracks. According toan embodiment, drains of the low-side power switches are electricallyconnected to the second group of power switch conductive tracks, and thethermal vias electrically couple the discrete conductive tracks to therespective ones of the second group of power switch conductive tracks.

According to an embodiment, electronic module further includes a slidingmember supported within the module housing and coupled to an actuatoroutside the module housing, where the actuator causing movement of thesliding member in a direction substantially perpendicular to thelongitudinal axis of the circuit board. The electronic module furtherincludes a first conductive body mounted on the first surface of thecircuit board and including a terminal tab coupled to the positive nodeof the power supply, a second conductive body mounted on the firstsurface of the circuit board in electrical contact with the mainconductive track, and a contact switch supported by the first conductivebody and pivotably moveable by the sliding member to make contact withthe second conductive body with movement of the actuator. According toan embodiment, the second conductive body is mounted on the mainconductive track.

According to an embodiment, the first conductive body includes a firstpin received through a first through-hole of the circuit board to makeelectrical contact with a first conductive track on the second surfaceof the circuit board, and the second conductive body includes a secondpin received through a second through-hole of the circuit board to makeelectrical contact with a second conductive track on the second surfaceof the circuit board. According to an embodiment, the electronic modulefurther comprises a flyback diode mounted on the second surface of thecircuit board electrically connected between the first conductive trackand the second conductive track.

According to an embodiment, electronic module includes a controller anda gate driver arranged on the second surface of the circuit board, wherethe controller is configured to control a switching operation of thepower switches via the gate driver.

According to an embodiment, a series of motor terminals is disposedalong a peripheral side parallel to the longitudinal axis of the circuitboard and electrically coupled to the power switches. According to anembodiment, the heat sinks are disposed along two rows parallel to thelongitudinal axis of the circuit board, one of the two rows beingadjacent the plurality of motor terminals. According to an embodiment,the power switches are connected to the motor terminals via intermediaryconductive tracks disposed in an intermediary layer of the circuitboard.

According to an embodiment, a power tool is provided including a housinghaving a motor housing and a handle portion. The handle portion housesan electronic module as described above, and the motor housingsupporting the electric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention will become more fullyunderstood from the detailed description given herein below and theaccompanying drawings, wherein like elements are represented by likereference numerals, which are given by way of illustration only and thusare not limitative of the example embodiments of the present invention.

FIG. 1 depicts a longitudinal cross-sectional view of a power tool witha housing half removed, according to an embodiment;

FIG. 2 depicts an exemplary block circuit diagram for an electroniccontrol module for controlling the power tool motor, according to anembodiment;

FIG. 3 depicts a perspective view of the electronic control module,according to an embodiment;

FIG. 4 depicts an exploded view of the electronic control module,according to an embodiment;

FIG. 5 depicts a top perspective view of a Printed Circuit Board (PCB)and the input unit, including the power contact switch, mounted thereon,according to an embodiment;

FIG. 6 depicts a bottom perspective view of the PCB, including a flybackdiode mounted thereon opposite the power contact switch, according to anembodiment;

FIG. 7 depicts a top exploded view of the PCB and the input unit,including the power contact switch, according to an embodiment;

FIGS. 8 and 9 depict perspective views of the power contact switch,according to an embodiment; and

FIGS. 10 and 11 depict perspective views of the upper and lower surfaceof the PCB, according to an embodiment.

DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

With reference to the FIG. 1, a power tool 100 constructed in accordancewith the teachings of the present disclosure is illustrated in alongitudinal cross-section view. Power tool 100 in the particularexample provided may be a hand held dill, but it will be appreciatedthat the teachings of this disclosure is merely exemplary and the powertool of this invention could be any power tool. The power tool shown inFIG. 1 may include a housing 102, an electric motor 104, a batteryreceptacle for receiving a removable battery pack 108, a transmissionassembly (gear case) 114, and an output spindle (not shown) driving achuck 116. The gear case 114 may be removably coupled to the housing102. The housing 102 can define a motor housing 111 and a handle 112.

According to an embodiment, motor 104 includes a stator 106 received inmotor housing 111. Motor 104 maybe be any type of motor and may bepowered by an appropriate power source. In an embodiment, the motor is abrushless DC electric motor including stator 106 and a rotor rotatablyreceived within the stator 106, and is powered by battery pack 108.

According to an embodiment of the invention, power tool 100 furtherincludes an integrated electronic switch and control module 200(hereinafter also referred to as “electronic control module”, or“control module”). Electronic control module 200, in an embodiment, mayinclude a controller and electronic switching components for regulatingthe supply of power from the battery pack 108 to motor 106. In anembodiment, electronic control module 200 is disposed within the handle112 below the motor housing 111, though it must be understood thatdepend on the power tool shape and specifications, electronic controlmodule 200 may be disposed at any location within the power tool.Electronic control module may also integrally include components tosupport a user-actuated input unit 110 (hereinafter referred to as“input unit” 110) for receiving user functions, such as an on/offsignal, variable-speed signal, and forward-reverse signal. In anembodiment, input unit 100 may include a variable-speed trigger 120,although other input mechanism such as a touch-sensor, acapacitive-sensor, a speed dial, etc. may also be utilized. In anembodiment, an on/off signal is generated upon initial actuation of thevariable-speed trigger 120. In an embodiment, a forward/reverse button122 is additionally provided on the tool 100. The forward/reverse button122 may be pressed on either side of the tool in a forward, locked, orreverse position. In an embodiment, the associated circuitry andcomponents of the input unit 110 that support the variable-speed trigger120 and the forward/reverse button 122 may be fully or at leastpartially integrated into the electronic control module 200. Based onthe input signals from the input unit 110 and associated components, thecontroller and electronic switching components of the electronic controlmodule 200 modulate and regulate the supply of power from the batterypack 108 to motor 106. Details of the electronic control module 200 arediscussed later in detail.

While in this embodiment, the power source is battery pack 108, it isenvisioned that the teachings of this disclosures may be applied to apower tool with an AC power source. Such a power tool may include, forexample, a rectifier circuit coupled to the AC power source.

It must be understood that, while FIG. 1 illustrates a power tool drillhaving a brushless motor, the teachings of this disclosure may be usedin any power tool, including, but not limited to, drills, saws, nailers,fasteners, impact wrenches, grinders, sanders, cutters, etc. Also,teachings of this disclosure may be used in any other type of tool orproduct that include a rotary electric motor, including, but not limitedto, mowers, string trimmers, vacuums, blowers, sweepers, edgers, etc.

The electronic control module 200 is described herein, according to anembodiment of the invention.

Referring to FIG. 2, a circuit block diagram of power tool 100 includingmotor 104 and electronic control module 200 is depicted, according to anembodiment.

In an embodiment, electronic control module 200 includes the input unit110, a power unit 207 and a control unit 209. In FIG. 2, power tool 100received DC power from a DC power source such as a battery pack via B+and B− terminals.

In an embodiment, power unit 207 may include a power switch circuit 205coupled between the power source B+/B− terminals and motor windings todrive BLDC motor 104. In an embodiment, power switch circuit 205 may bea three-phase bridge driver circuit including six controllablesemiconductor power devices (e.g. FETs, BJTs, IGBTs, etc.).

In an embodiment, control unit 209 may include a controller 218, a gatedriver 219, and a power supply regulator 221. In an embodiment,controller 218 is a programmable device arranged to control a switchingoperation of the power devices in power switching circuit 226. In anembodiment, controller 218 receives rotor rotational position signalsfrom a set of position sensors 203 provided in close proximity to themotor 104 rotor. In an embodiment, position sensors 203 may be Hallsensors. It should be noted, however, that other types of positionalsensors may be alternatively utilized.

In an embodiment, controller 218 is activated by the input unit 110 uponthe initial actuation of the trigger 120. The input unit 110 alsoprovides a variable voltage signal indicative of the displacement of thetrigger 120 to the controller 218. Based on the rotor rotationalposition signals from the position sensors 203 and the variable voltagesignal, controller 218 outputs drive signals UH, VH, WH, UL, VL, and WLthrough the gate driver 219, which provides a voltage level needed todrive the gates of the semiconductor switches within the power switchcircuit 205 in order to control a PWM switching operation of the powerswitch circuit 205.

In an embodiment, power supply regulator 221 may include one or morevoltage regulators to step down the power supply to a voltage levelcompatible for operating the controller 218 and/or the gate driver 219.In an embodiment, power supply regulator 221 may include a buckconverter and/or a linear regulator to reduce the power voltage ofbattery down to, for example, 15V for powering the gate driver 219, anddown to, for example, 3.2V for powering the controller 218.

In an embodiment, electronic control module 200 includes components andcircuitry associated with the user-actuated input unit 110. Suchcomponents may detect a movement of the trigger 120 and initiate asignal to turn on the controller and other components of electroniccontrol module 200. In an example, as described in U.S. Pat. No.9,508,498, content of which is incorporated herein by reference in itsentirety, electronic control module 200 may include a series ofconductive pads coupled to a series of resistors that output variousvoltages based on the position of a wiper coupled to the trigger switch.Upon initial engagement of the trigger switch, the output voltage signal(referred to as the WIPER signal in FIG. 12 of the '498 patent, and asthe switch signal hereinafter) exhibits a prescribed change in voltagethat, though associated circuitry, couples the controller to batterypower supply and turns the controller on.

In an embodiment, the switch signal may be active high, meaning that ahigh voltage signal is generated on the switch signal when the triggeris pressed. Alternatively, and consistent with FIG. 12 of the '498patent discussed above, the switch signal may be active low, meaningthat the voltage signal on Switch Signal is normally a high voltage(e.g., equivalent to the battery voltage), that changes to a lowervoltage amount when the trigger is pressed.

In an embodiment, electronic control module 200 is provided with a powercontact switch 300 and a flyback diode 340 disposed in parallel to thepower contact switch 300. Power contact switch 300 is a contact ON/OFFswitch coupled to the trigger 120 and/or the input unit 110. Asdescribed later in this disclosure, initial actuation of the trigger 120closes the power contact switch 300. Power contact switch 300 in thisembodiment disables supply of power from the B+ node of the batteryterminal to the power switch circuit 205. It is noted, however, thatpower switch 300 may be provided at a different location, for example,on the B− node of the battery terminal, between one node of the batteryand the power supply regulator 221, between the power supply regulator221 and the gate drivers 232, etc. Power contact switch 300 provides asecondary safety mechanism that ensure that power to the motor 104 iscut off when the trigger 120 is not actuated by the user, even if any ofthe electronic components (i.e., the electro-mechanical components ofthe input unit 110, the controller 218, the gate driver 219, or thepower switch circuit 205) experience failure. In an embodiment, flybackdiode 340 provides a current path for the back-EMF of the motor 104 toflow back to the battery pack, for example, during motor coast or motorbraking, when power contact switch 300 is open.

Electronic control module 200 is described herein with reference toFIGS. 3-6. FIG. 3 depicts a perspective view of the electronic controlmodule 200, according to an embodiment. FIG. 4 depicts an exploded viewof the electronic control module 200, according to an embodiment. FIG. 5depicts a top perspective view of a Printed Circuit Board (PCB) 202 andthe input unit 110 of the electronic control module 200, according to anembodiment. FIG. 6 depicts a bottom perspective view of the PCB 202 andthe input unit 110, according to an embodiment.

In summary, in an embodiment, electronic control module 200 generallyincorporates elements of the input unit 110, power unit 207 (includingpower switches 208 configured as an inverter-switch circuit in powerswitch circuit 205), and control unit 209 (including controller 218,gate driver 219, power supply regulator 221). In an embodiment,electronic control module 200 further includes power contact switch 300and flyback diode 340 actuated by the input unit 110.

In an embodiment, electronic control module 200 includes a printedcircuit board (PCB) 202 arranged and mounted inside a module housing204. Module housing 204 includes a bottom surface 227, side walls 228,and an open face. PCB 202 is received through the open face and securedinside the module housing 204. Side walls 228 include retention features229 for securely holding the PCB 202 at a distance from the bottomsurface 227. Electronic control module 200 includes two compartments—anenclosed compartment 210 a that houses and encloses a first part of thePCB 202 and components associated with the input unit 110, and an opencompartment 210 b, and partially encloses a second part of the PCB 202.Within the open compartment 210 b, module housing 204 encloses the lowersurface and the sides of PCB 202, but leaves the upper surface of thePCB 202 substantially exposed to airflow. Mounted on a bottom surface ofPCB 202 are power switches 208 (which are connected as an invertercircuit to make up the power switch circuit 205), and mounted on a topsurface of the PCB 202 are a series of heat sinks 206 disposed oppositethe power switches 208. The heat sinks 206 are discretely mounted overthe PCB 202 in thermal communication with the power switches 208. Asdiscussed below in detail, this arrangement allows cooling air totransfer heat away from the power switches 208 to the outsideenvironment via the heat sinks 206 while protecting the power switches208 within an enclosed space of the electronic switch module 200. In anembodiment, the gap between the PCB 202 and the bottom surface 227 ofthe module housing 204 is filled with potting material thatsubstantially cover the power switches 208 and other components.

In an embodiment, controller 218 is mounted to a lower surface of thePCB 202 and is in electronic communication with gate driver 219, powersupply regulator 221 and the rest of the PCB 202 components throughmetal routings and/or conducive vias. Controller 218 may be programmedto turn on and off power switches 208, as discussed below, to controlcommutation of the brushless motor.

In an exemplary embodiment, power switches 208 may be Field EffectTransistors (FETs). In an embodiment, six power switches 208, includingthree high-side power switches and three low-side power switches, arearranged and coupled together as a three-phase bridge rectifier circuit.Using the gate driver 219, controller 218 sequentially turns the powerswitches 208 on and off within each phase of the brush motor 104commutation. Further, the controller 218 performs pulse-width modulation(PWM) of the power switches 208 within each phase to regulate the speedof the motor based on speed signals received from input unit 110, asdescribed below. Controller 218 further controls the direction of motorcommutation based on a forward/reverse signal received from input unit110, also discussed below.

It is noted that while the power switches 208 discussed herein are FETs,other types of power switches such as BJTs or IGBTs may be utilized.Additionally, while power switches 208 are arranged as a three-phasebridge rectifier for driving a three-phase brushless motor, other numberand arrangement of power switches may be used to drive other types ofmotors, including brushed or brushless motors.

As described above, module housing 204 leaves the upper surface of thePCB 202 exposed, thus allowing heat to dissipate from the heat sinks206. Electronic control module 200 may be placed within a path of airflow inside the power tool, e.g., inside the power tool handle 112 influid communication with motor fan 106 so that airflow generated bymotor fan 106 runs through the handle 112. The air flow generated withinthe handle further improves heat dissipation from the electronic controlmodule 200.

In an embodiment, the PCB 202 is further potted with a layer of pottingcompound (not shown) in the open compartment 210 b. The layer of pottingcompound, in an embodiment, substantially covers most of the circuitcomponents on the PCB, but leave a top plate of heat sinks 206 exposedso the heat sinks 206 can dissipate heat away from the power switches208.

In an embodiment, a bottom surface area of each heat sink 206 has asurface area of 10 to 40 mm², preferably 15-35 mm², more preferably20-30 mm². This bottom surface is fully mounted on the PCB 202. In anembodiment, each heat sink 206 is in thermal communication with acorresponding one of the power switches 208 via a series of thermalvias. Additionally, in an embodiment, some or all the thermal vias maybe electrically conductive, allowing each heat sink 206 to beelectrically connected to the drain of the corresponding power switch208 for more efficient thermal transfer.

In an embodiment, a series of output wires 212 are secured on one end toa surface of the PCB 202. These wires connect the outputs of the powerswitch circuit 205 (i.e., power switches 208) to the power terminals thebrushless motor 104. In an embodiment, a series of control signal wires214 are also secured to a connector 241 on the PCB 202. The controlsignal wires 214 allow the controller 218 to communicate with otherparts of the power tool 100, such as the motor 104 and the battery 108.In an embodiment, hall signals from the brushless motor positionalsensors 203 are coupled via ribbon connector 215 to the control signalwires 214 to communicate with the controller 218. In an embodiment, apair of power input wires 217 are also secured on the surface of PCB202. These wires are coupled to a power source (e.g., battery 108) via apower terminal 216 to supply power from the power source to the powerswitches 208.

In an embodiment, control module 200 includes an encapsulation member260 that mates with the module housing 204 to form the enclosedcompartment 210 a of control module 200. Encapsulation member 260 formsthe first compartment 210 a to protect components associated with inputunit 110 from dust and debris. Details relating to the encapsulationmember 260 may be found in US Patent Publication No. 2015/0280516, whichis incorporated herein by reference in its entirety.

In an embodiment, control module 200 includes an additional cover 270that covers a lower portion of PCB 202. Cover 270 also includes wireretaining features for retaining the power wires 217, as well as wireguide features for guiding the wires 217 around circuit components(e.g., capacitors 272) mounted on PCB 202.

The input unit 110 is discussed herein, according to an embodiment ofthe invention. According to an embodiment, input unit 110 is at leastpartially integrated into control module 200. In an embodiment, inputunit 110 incorporates electro-mechanical elements for variable-speeddetection, on/off detection, and forward/reverse detection inside theenclosed compartment 210 a of control module 200, as discussed herein.

In an embodiment, input unit 110 includes a forward/reverse actuator 220supported by the enclosed compartment 210 a portion of the modulehousing 204. In an embodiment, forward/reverse actuator 220 pivotablymakes or break contact between a pair of conductive tracks on the PCB202, which is sensed by the controller 218. U.S. Pat. No. 9,508,498filed May 21, 2012, which is incorporated herein by reference in itsentirety, describes such a forward/reverse detection mechanism in moredetail.

According to an embodiment, input unit 110 further includes avariable-speed actuator 230. Variable-speed actuator 230 includes a linkmember 282 that extends out of the module housing 204 from a slidingmember 280. Link member 282 is securely coupled to trigger 120 that isengageable by the user. Sliding member 280 is arranged inside the modulehousing 204 and includes a main body 284 that supports a conductivewiper 290 at its lower surface. The sliding member 280 further includesa pocket 286 that supports and engages a compression spring 292 receivedthrough its longitudinal end opposite link member 282. Compressionspring 292 is located between an inner wall of the module housing 204and the sliding member 280. When the user presses the trigger 120, thesliding member 280 moves against a biasing force of the spring 292. Thesliding member 284 further includes a rib 288 as described later.

In an embodiment, conductive wiper 290 contacts a speed-sensing memberlocated on the surface of the PCB 202. In an embodiment, thespeed-sensing member is a series of variable-speed conductive tracks 240arranged on the PCB 202. Actuation of the trigger 120 moves theconductive wiper 290 over the conductive tracks 240. Initial movement ofthe conductive wiper 290 over the conductive tracks 240 generates asignal that turns controller 218 ON. Additionally, an analogvariable-voltage signal is generated based on the movement of theconductive wiper 290 over the conductive tracks 240 and that signal issent to the controller 218. This signal is indicative of the desiredmotor speed. Functional details of ON/OFF and variable-speed detectionusing conductive tracks 240 are discuss in U.S. Pat. No. 9,508,498 filedMay 21, 2012, which is incorporated herein by reference in its entirety.It must be understood, however, that any known variable-voltagespeed-sensing mechanism, such as a resistive tape, may be a utilizedwithin the scope of the invention.

In an embodiment, electronic control module 200 is further provided withpower contact switch 300 on the upper surface of the PCB 202. As shownin FIG. 2, power contact switch 300 is disposed on the current path fromthe battery terminal B+ to electrically cut off supply of power to thepower switch circuit 205. In an embodiment, flyback diode 340 disposedon the lower surface of the PCB 202 and electrically connected inparallel to the power contact switch 300.

Referring to FIG. 7-9, and with continued reference to FIGS. 3-6, powercontact switch 300 is described herein.

In an embodiment, power contact switch 300 includes a first conductivebody 310, a contract switch 320, and a second conductive body 330.

In an embodiment, first conductive body 310 is secured on the uppersurface of the PCB 202 via a first pin 312 that is received through afirst through-hole 302 of the PCB 202. A terminal tab 314 extendsdownwardly from an upper portion of the first conductive body 310.Terminal tab 314 extends out of the encapsulation member 260 and isattached to one the B+ power line of the power input wires 217 (see FIG.3).

In an embodiment, second conductive body 330 is secured on the uppersurface of the PCB 202 via a second pin 332 received through a secondthrough-hole 304 of the PCB 202. The second conductive body 330 includesa contact portion 334 positioned in close proximity to the firstconductive body 310.

In an embodiment, contact switch 320 is pivotably attached to the firstconductive body 310 via a pivot attachment 322, which electricallyconnects the contact switch 320 to the first conductive body 310.Contact switch 320 includes an engagement leg 326 and a contact leg 328arranged at approximately a right angle with respect to one another. Thepivot attachment 322 is coupled to the attachment point of theengagement leg 326 and the contact leg 328. A compression spring 324 isdisposed between the engagement leg 326 and an extension portion 316 ofthe first conductive body 310. Compression spring 324 biases theengagement leg 326 into contact with contact portion 334 of the secondconductive body 330. In an embodiment, the biasing force of the spring324 is less than that of the spring 292.

In an embodiment, as briefly described above, sliding member 272 of theinput unit 110 includes a rib 288. Rib 288 is disposed along an axisnormal to a plane of the PCB 202 and is disposed over the main body 284of the sliding member 272 opposite the conductive wiper 290. In anembodiment, the rib 288 engages the engagement leg 326 when the trigger120 is released and the sliding member 272 is moved via the biasingforce of the spring 292. The rib 288 in this position forces the contactswitch 320 to pivot around the pivot attachment 322 against the biasingforce of the spring 324, thus breaking contact between the contact leg328 of the contact switch 320 and the contact portion 334 of the secondconductive body 330. In this manner, when the trigger 120 is released,rib 288 breaks contact between the first and second conductive bodies310 and 330. When the trigger 120 is pressed, the rib 288 disengages theengagement leg 326, and spring 324 biases the contact leg 238 intocontact with the contact portion 334 of the second conductive body 330.

In an embodiment, as briefly described above and shown in FIG. 6,flyback diode 340 is mounted on the lower surface of the PCB 202opposite the power contact switch 300. In an embodiment, flyback diode340 is electrically connected via conductive tracks provided on thelower surface of the PCB 202 between first pin 312 and second pin 332.In this manner, flyback diode 340 is electrically coupled in parallelacross the power contact switch 300.

Referring to FIGS. 2, 6 and 7, a main conductive track 306 and a groundconductive track 308 are coupled to the + and − terminals of powerswitches 208 of the power switch circuit 205. Positive conductive track306 is disposed around through-hole 304 and is thus electricallyconnected to the second conductive body 330 of the power contact switch300. In an embodiment, ground conducive track 308 is coupled to one ofthe power input wires 217 to receive the B− power line from the battery.

FIGS. 10 and 11 depict zoomed-in perspective views of the upper andlower surfaces of the PCB 202 without the power switches 208 and heatsinks 206, according to an embodiment. As shown herein, lower conductivetracks 303 and 305 on the lower surface of the PCB 202 couple the pins332 and 312 to the flywheel diode 340.

In an embodiment, in the axial direction A of the PCB 202 towards theinput unit 110, a traversal portion of the main conductive track 306 isdisposed downstream of the heat sinks 206, and an axial portion of themain conductive track 306 is disposed in-line with the heat sinks 206along the axis A to provide a mounting surface for three of the(high-side) heat sinks 206. In an embodiment, the three high-side heatsinks 206 are at the same electrical potential as the + node of thepower switch circuit 205. In an embodiment, ground conductive track 308is disposed upstream of the heat sinks 206 in the axial direction A ofthe PCB 202.

In an embodiment, traversal portion of the main conductive tracks 306 onthe upper surface of the PCB is electrically connected to lowerconductive track 305 via a series of conductive vias. In an embodiment,the axial portion of the main conductive track 306, which extends underthe three of the (high-side) heat sinks 206, is connected to powerswitch conductive tracks 380 on the lower surface of the PCB 202. Threehigh-side power switches 208 are mounted on the lower surface of the PCB202 at least partially over corresponding power switch conductive tracks380, with the drains of the high-side power switches 208 makingelectrical contact with corresponding power switch conductive tracks380. This arrangement allows the three (high-side) heat sinks 206 to beelectrically connected to the drains of the high-side power switches 208via main conductive track 306 and power switch conductive tracks 380,thus increasing thermal conductivity from the high-side power switches208. In an embodiment, a series of 12 conductive vias are arrangedbetween each power switch conductive track 380 and the main conductivetrack 306 to thermally connect each high-side power switch 208 to thecorresponding heat sinks 206.

In an embodiment, three discrete conductive tracks 382 are provided onthe upper surface of the PCB 202, on which three of the (low-side) heatsinks 206 are mounted. Opposite the discrete conductive tracks 382 areprovided three power switch conductive tracks 384. The low-side powerswitches 208 are mounted at least partially on the three power switchconductive tracks 384. In an embodiment, drains of the low-side powerswitches 208 are electrically connected to the three power switchconductive tracks 384 for increased thermal transfer. Discreteconductive tracks 382 and power switch conductive tracks 384 areelectrically connected via a series of conductive vias (in this example,12 vias per heat sink 206). These conductive vias may be electricallyand/or thermally conductive to increase thermal conductivity from thelow-side power switches 208 to the corresponding heat sinks 206.

In an embodiment, corresponding high-side and low-side power switches208 are connected as an inverter circuit via intermediary conductivetracks (not shown) disposed in an intermediary layer of the PCB 202 tomotor terminals 386 disposed along a peripheral side of the PCB 202adjacent and parallel to the power switches 208. Output wires aresecured, via, for example soldering or other known method, to theterminals 386. Arrangement of the motor terminals 386 on along theperiphery of the PCB 202, rather than, for instance, between thecorresponding power switches 208, eases the manufacturing and assemblyprocess. Additionally, this arrangement allows disposition of largerconductive tracks on the terminals 386, which carry high motor current,and thus increase thermal efficiency of the power switch circuit 205.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” “bottom,” “lower,” and the like, may be usedherein for ease of description to describe one element or feature'srelationship to another element(s) or feature(s) as illustrated in thefigures. Spatially relative terms may be intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the example term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

1. An electronic module comprising: a circuit board defining alongitudinal axis and having a first surface and a second surface; amodule housing having a bottom surface and a plurality of side wallsextending from the bottom surface to form an open face, the modulehousing receiving the circuit board through the open face and retainingthe circuit board within the side walls substantially parallel to thebottom surface and at a distance from the bottom surface; a plurality ofpower switches configured as an inverter circuit to supply power from apower supply to an electric motor and mounted on the second surface ofthe circuit board facing the bottom surface of the module housing; aplurality of heat sinks discretely mounted on the first surface of thecircuit board facing the open face, the plurality of heat sinks beingarranged opposite the plurality of power switches; potting materialdisposed in the distance between the circuit board and the bottomsurface of the module housing to cover the plurality of power switches;and a plurality of thermal vias disposed through the circuit boardbetween corresponding ones of the plurality of heat sinks and theplurality of power switches.
 2. The electronic module of claim 1,wherein the plurality of power switches comprises a plurality ofhigh-side power switches disposed between a positive node of a powersupply and the electric motor, and a plurality of low-side powerswitches disposed between a negative node of the power supply and theelectric motor.
 3. The electronic module of claim 2, further comprisinga main conductive track disposed on the first surface of the circuitboard providing a mounting surface for three of plurality of heat sinkscorresponding to the high-side power switches, the main conductive trackelectrically coupling the three heat sinks corresponding to thehigh-side power switches to the positive node of the power supply. 4.The electronic module of claim 3, wherein the main conductive trackincludes an axial portion that extends along the longitudinal axis ofthe circuit board and on which three of the plurality of heat sinks aremounted, and a traversal portion arranged downstream from the pluralityof heat sinks in the direction of the longitudinal axis of the circuitboard.
 5. The electronic module of claim 3, further comprising aplurality of discrete conductive tracks being electrically-isolated anddisposed on the first surface of the circuit board along a rowsubstantially parallel to the longitudinal axis of the circuit board,the plurality of discrete conductive tracks providing mounting surfacesfor three of the plurality of heat sinks corresponding to the low-sidepower switches.
 6. The electronic module of claim 5, further comprisinga first plurality of power switch conductive tracks disposed on thesecond surface of the circuit board opposite the main conductive trackto provide mounting surfaces for the plurality of high-side powerswitches, and a second plurality of power switch conductive tracksdisposed on the second surface of the circuit board opposite the row ofthe plurality of discrete conductive tracks to provide mounting surfacesfor the plurality of low-side power switches.
 7. The electronic moduleof claim 6, wherein drains of the plurality of high-side power switchesare electrically connected to the first plurality of power switchconductive tracks, and the plurality of thermal vias electrically couplethe main conductive track to the first plurality of power switchconductive tracks.
 8. The electronic module of claim 6, wherein drainsof the plurality of low-side power switches are electrically connectedto the second plurality of power switch conductive tracks, and theplurality of thermal vias electrically couple the plurality of discreteconductive tracks to the respective ones of the second plurality ofpower switch conductive tracks.
 9. The electronic module of claim 3,further comprising: a sliding member supported within the module housingand coupled to an actuator outside the module housing, the actuatorcausing movement of the sliding member in a direction substantiallyperpendicular to the longitudinal axis of the circuit board; a firstconductive body mounted on the first surface of the circuit board andincluding a terminal tab coupled to the positive node of the powersupply; a second conductive body mounted on the first surface of thecircuit board in electrical contact with the main conductive track; anda contact switch supported by the first conductive body and pivotablymoveable by the sliding member to make contact with the secondconductive body with movement of the actuator.
 10. The electronic moduleof claim 9, wherein the second conductive body is mounted on the mainconductive track.
 11. The electronic module of claim 9, wherein thefirst conductive body includes a first pin received through a firstthrough-hole of the circuit board to make electrical contact with afirst conductive track on the second surface of the circuit board, thesecond conductive body includes a second pin received through a secondthrough-hole of the circuit board to make electrical contact with asecond conductive track on the second surface of the circuit board, andthe electronic module further comprises a flyback diode mounted on thesecond surface of the circuit board and electrically connected betweenthe first conductive track and the second conductive track.
 12. Theelectronic module of claim 1, further comprising a controller and a gatedriver arranged on the second surface of the circuit board, thecontroller being configured to control a switching operation of theplurality of power switches via the gate driver.
 13. The electronicmodule of claim 1, comprising a plurality of motor terminals disposedalong a peripheral side parallel to the longitudinal axis of the circuitboard, the plurality of motor switches being electrically coupled to theplurality of power switches.
 14. The electronic module of claim 13,wherein the plurality of heat sinks is disposed along two rows parallelto the longitudinal axis of the circuit board, one of the two rows beingadjacent the plurality of motor terminals, and wherein the plurality ofpower switches is connected to the plurality of motor terminals via aplurality of intermediary conductive tracks disposed in an intermediarylayer of the circuit board.
 15. A power tool comprising: a housingincluding a motor housing and a handle portion, the handle portionhousing an electronic module according to claim 1, and the motor housingsupporting the electric motor.